Investigation on the Reactions of Small Ring Ion Radicals and their Application to Synthetic Reactions

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1. The photosensitized one electron oxidation of three deuterium-labeled and alkyl substituted bicyclo[2.2.0]hexanes afforded 1,5-hexadienes predominantly with the retention of configuration, which indicated that intermediate cyclohexane-1,4-diyl cation radicals underwent ring cleavage in the boat conformation which was separated from the chair and/or twist-boat conformation by a sizable energy barrier. The dependence of the stereospecificity of ring fission on the reduction potential of electron acceptor implied that the ring cleavage and back electron transfer in the radical ion pairs were competitive in rate.2. 4-Thiadispiro[2.1.2.2]non-8-ene and several spiro-cyclopropylfluorenes were synthesized and their reactivities toward electron deficient compounds were examined. The former compound underwent cycloadditions with TCNQ and TCNE in which the use of ethereal solvent was critical and afforded thiophenophane derivatives.3. The behavior of some 1,4-bridged Dewar benzene derivatives under the conditions of photosensitized one electron oxidation was studied. They underwent the cleavage of central sigma bond to give bent benzene cation radicals to which nucleophiles added. In the process of study, we also succeeded in generating the most highly bent benzene derivative-[4]paracyclophane, a novel, fully conjugated bicyclic system-bicyclo[4.2.2]decapentaene, and an ortho quinoidal tropone derivative-3,4-benzotropone.